It appears that Napoleon looked to only threaten the Channel Islands as a means to force the British to maintain a naval and army presence thereby reducing its forces for service elsewhere.

Some details of the defence of the islands can be found in, Man of War: The Fighting Life of Admiral James Saumarez: From The American Revolution to the Defeat of Napoleon. Anthony Sullivan. Frontline Books 2017. Saumarez was the Naval Commander-in-Chief of the Channel Islands 1803-1808.